Certain guanine-N-oxides, particularly the N.sup.1 -, N.sup.3 -, and N.sup.9 -oxides have been known in the literature for some time. G. B. Brown and his co-workers have conducted a series of studies on guanine-N-oxides.
In 1965, Brown, et al. [Cancer Research, 25:986-991 (1965)] reported the oxidation of guanine with hydrogen peroxide in trifluoroacetic acid to produce an unidentified N-oxide having oncogenic properties.
In a later paper, Delia and Brown (J. Org. Chem., 31:178-181 (1966)] reported their conclusions that the unidentified guanine-N-oxide was the N.sup.7 -oxide, compound Ia. ##STR1##
Subsequently, Brown suggested [Cancer Research, 27:925-931 (1967)] that the material which they had produced which exhibited oncogenic properties was the 7-hydroxyguanine tautomer, Ib. However, Wolcke and Brown [J. Org. Chem., 34:978-981 (1969)] showed that the guanine N-oxide which they had reported and discussed in the earlier papers was not guanine-N.sup.7 -oxide, but was instead guanine-N.sup.3 -oxide, compound II. The incorrect structure had been assigned to the material which they had produced on the basis of the infrared spectrum of a known degradation product.
In addition to the above-described synthesis of guanine-N.sup.3 -oxide, the synthesis of guanine-N.sup.1 -oxide [Brown, et al., J. Org. Chem., 38:3046-3048 (1973)] and guanine-N.sup.9 -oxide [Watson, J. Org. Chem., 39:2911-2916 (1974)] have also reported.